Primary somatosensory cortex oscillations in trigeminal neuralgia: laser-evoked signatures and their potential relevance to microvascular decompression

Classical trigeminal neuralgia (TN) is a severe chronic pain disorder characterized by sudden, intense facial pain attacks and represents a major burden for affected individuals. Microvascular decompression (MVD) can provide pain relief, yet not all patients benefit equally. A key challenge in selecting candidates for MVD lies in the limited predictive accuracy of current diagnostics, which mainly rely on subjective pain history and structural MRI findings. Since many asymptomatic individuals show neurovascular contact on imaging, its prognostic value remains limited. Electrophysiological measures, particularly cortical oscillations, may offer more objective insights into nociceptive system function. In this case series, we investigated 15 TN patients scheduled for MVD using magnetoencephalography prior to surgery to assess laser-evoked fields. Noxious stimuli were applied to the symptomatic and contralateral trigeminal dermatome. Ten patients achieved complete postoperative pain relief (responders), while five patients reported persistent symptoms (non-responders). Source reconstruction showed activation in the contralateral primary somatosensory cortex in all participants. Responders exhibited reduced low-frequency oscillatory activity at the pain site, whereas non-responders displayed increased activity in the same frequency band. Group-level analysis revealed distinct differences in oscillatory dynamics between responders and non-responders. These findings indicate altered cortical processing in TN and suggest that oscillatory activity patterns might serve as functional biomarkers. Incorporating these measures could improve preoperative stratification and guide treatment decisions for patients undergoing MVD.